Porous Carbon-Silicon Anode Particles for Capacity Retention
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Solution Overview
Problem
Current methods for preparing composite materials with high electrochemical capacities for use in rechargeable metal-ion batteries face challenges in maintaining capacity over charge-discharge cycles due to volume changes and mechanical stress, particularly with silicon anodes, which experience significant expansion and contraction, leading to fracturing and loss of electrochemical capacity.
Innovation Solution
A process involving chemical vapour infiltration (CVI) into a fluidised bed reactor using porous carbon frameworks with specific pore structures and particle sizes, followed by comminution, to deposit electroactive materials like silicon within the carbon framework, creating a stable and efficient nanostructure suitable for large-scale commercial production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode material to achieve high capacity, then gravimetric and volumetric capacities are improved, but volume changes and mechanical stress cause fracturing and capacity loss over cycles
Solution Approach 1:
The silicon anode material is divided into fine particles with D50 diameter of 3-15 μm, which reduces the overall volume change impact and prevents large-scale fracturing. The segmented structure allows better accommodation of expansion/contraction stresses while maintaining capacity.
Solution Approach 2:
The patent applies different properties to different parts of the silicon structure by creating a coated or composite structure where silicon is combined with other materials (such as carbon coatings or matrix materials) that provide mechanical stability while silicon provides high capacity. This local differentiation allows simultaneous achievement of high capacity and structural stability.
2Reliability
If chemical vapour infiltration is used to deposit electroactive material into porous carbon frameworks, then structural robustness and capacity retention are improved, but additional process steps increase manufacturing complexity
Solution Approach 1:
Porous carbon frameworks serve as an intermediary structure that facilitates the deposition of electroactive materials through chemical vapour infiltration. The carbon framework acts as a template and support structure, enabling controlled deposition while providing mechanical stability. This intermediary approach simplifies the overall manufacturing by using a self-organizing template rather than requiring direct complex assembly.
Solution Approach 2:
The patent replaces traditional mechanical mixing or assembly methods with chemical vapour infiltration, where electroactive materials are deposited through chemical reactions in the vapor phase. This substitution of mechanical processes with chemical processes enables more uniform distribution and better integration of materials while reducing mechanical stress and complexity.
3Reliability
If fine silicon particles are used to reduce volume change impact, then capacity retention is improved, but handling and processing difficulties increase
Solution Approach 1:
The patent uses composite materials where fine silicon particles are combined with porous carbon frameworks or other matrix materials. This composite structure maintains the benefits of fine silicon particles (reduced volume change impact) while the carbon framework or matrix material provides handling stability, prevents agglomeration, and facilitates processing. The composite nature solves both the performance and manufacturability issues.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in composite particles with improved capacity retention and structural robustness, enabling high gravimetric and volumetric capacities while minimizing damage during the comminution process, thus addressing the issues of volume changes and mechanical stress in silicon anodes.
Implementation Method 1
depositing an electroactive material selected from silicon, tin, aluminium, germanium and alloys thereof into the micropores and/or mesopores of the porous carbon frameworks using a chemical vapour infiltration process in a fluidised bed reactor
Implementation Method 2
chemical vapour infiltration process in a fluidised bed reactor
Data Source
AI summary
The disclosure relates to a process for preparing particulate materials having high electrochemical capacities that are suitable for use as anode active materials in rechargeable metal-ion batteries. In one aspect, the disclosure provides a process for preparing a particulate material comprising a plurality of composite particles. The process includes providing particulate porous carbon frameworks comprising micro pores and/or mesopores, wherein the porous carbon frameworks have a D50 particle diameter of at least 20 μm; depositing an electroactive material selected from silicon and alloys thereof into the micropores and/or mesopores of the porous carbon frameworks using a chemical vapour infiltration process in a fluidised bed reactor, to provide intermediate particles; and comminuting the intermediate particles to provide said composite particles.